Luminescent coating material



Patented Nov.27, i945 2,389,781

umruo STATES PATENT OFFICE 2,389,781 LUMINESCENT COATING MATERIAL Sampson Iscnberg, Chicago, Ill asslgnor to General Luminescent Corporation, Chicago, Ill, a corporation of Illinois No Drawing. Application June 22, 1942, Serial No. 447,932

15 Claims. (Cl. 252-30l.3)

My invention relates to surface covering prepvery quickly and become worthless as light emitarations using luminescent materials. It relates ters. I have found, for example, that if a zinc venting darkening of such pigments. under controlled test conditions, the life of the Certain types of luminescent materials are light pigment will be forty minutes and this notwithsensitive, particularly in the presence of moisture. standing the fact that methyl methacrylate resin When such luminescent materials are incorporati considered to have considerable value in proed in usual paint Vehicles and the resulting paint tecting surfaces and objects from atmosphere applied to a surface by any usual procedure such 7 and, moreover, is and has been considered a very as s n Sp ay g, screening, printin and desirable vehicle for use with luminescent pigthe like, the surface frequently becomes discolmerits. ored and blackened if exposed to sunlight for I have found that, under the same test condionly a relatively short period of time, particularly ticns. a f ce comprising he me l in n if moisture be present. Not only is the daylight material produced and applied in accordance character of the pigment affected adversely but with my invention, and which is at least as brilthe luminescent power of the pigment may be liant as the control sample when first produced,

various types of luminescent materials may be so hours under the same accelerated test conditions. affected, the more important ones with which this A useful life 125 times as long is readily obtained difiiculty occurs are the sulphides, particularly for the luminescent s W the P nt zinc sulphide, cadmium sulphide and mixed zinc pa tke bodies ar p du d in a an e with cadmium sulphide wherein th ratio of zinc to my invention and I believe, from the results obcadmium may vary from 1 to 10,000 to 10,000 to l, tained, that the useful life of a coating produced depending upon the color of the material desired. in accordance with my invention may be still fur- Such sulphides may be activated with various ther and markedly increased. substances such as copper, bismuth, manganese, In accordance with the general features of y nickel, and the like, the latter, in addition to being invention, I e, with the luminescent Pi m n an activator, having the function sometimes of and hi including a r, P i l ester decreasing phosphorescence or after-glow. of a relatively high molecular weight carboxyiic Luminescent material of the sulphide type acid and a po yhydric oxy substance. Among the have been used, for example, on the dials of airmaterials winch I have fo nd p r i a y D ane instruments, the desired effect being that isfactory in the practice of my invention are the the paint-like material comprising the luminesaliphatic carboxylic acid esters of po y y ri cent material has the same general daylight, cohols, particularly the mono ricinoleic acid ester color as the luminescent color at night when the of glycerin. Suit ly p y his Particular surface is subjected to ultra violet radiation. partial ester is very efiicacious formypurpose. I One way of, applying luminescent sulphide mahave also found that when certain resins, parterial for this purpose is in the form of a paint, 0 ticularly the alkyd resins, are employed as bindand for convenience I shall first direct my atteners, the effect of the partial ester in preventing tion to this type of vehicle. Paint pigments are or retarding the deleterious effect of light and generally ground to quite finely divided form and light and moisture on the l cent materials incorporated in a binder to give the proper conis greatly enhanced. I have found, also, that, in sistency and proper drying characteristics. The general, the coating ppli d y the use of my binder used, when the pigments are luminescent, invention remains somewhat soft for relatively is one which will admit sufficient ultra violet light long periods of time, and to protect the surface I through the binderto the pigmenttopermit actiutilize a thin coating of a resin, all as will be vation thereof. Paint of the type identified, aft r pointed ut in r at r detail. I have when applied to a surface, frequently biacken found that the protective coating referred to appears to have considerable advantage also in increasing the useful life of the coating and retarding the effect of the sunlight and moisture.

In accordance with one example, I produce a paint adapted for application to a surface by brushing in the following manner: 16 part of zinc cadmium sulphide activated with copper and previously ground to 200 mesh are mixed with 1.6 parts of glycerin mono-ricinoleate and 1.6 parts of a thinner which is compatible with both the glycerol monc-ricinoleate and an alkyd resin subsequently employed as a binder. This mixture is introduced into a ball mill and the ball mill operated for four hour to thoroughly coat all of the particles of zinc cadmium sulphide with the glycerol mono-ricinoleate. To the ground mixture is then added 28 parts by weight of an alkyd resin solution, the alkyd resin solution comprising 50% solid alkyd resins and 50% thinner. The thinner is a conventional type of commercial thinner, usually a mixture, but it may be, for example, one of the following: toluene, xylene, naphtha distillates," butyl acetate, amyl acetate, "mineral spirits and the like. This resulting mixture is then ground in a ball mill for about one hour and is ready for use. It is applied with a brush to surfaces on which it is to be used. The applied coating is allowed to dry for a suitable time, e. g.,' about 24 hours, and a protective coating of an acrylic acid resin is applied thereto. The coating is applied by dissolving acrylic acid resin in a solvent and applying the resulting solution by means of a spray or brush. The resin employed for this protective coating should be one which is compatible with the binder employed for the paint and one which will not block out ultra violet light. Nitrocellulose alone, in general, is not satisfactory but resin such as the alkyd, glyptal, methyl methacrylate, and like resins may be employed. Certain types of naturally occurring resins may, also, be used. The coating produced in accordance with the above example remained in good condition in excess of 90 hours during the accelerated test referred to hereinabove.

Another example of a method of practicing the invention is to mix together parts of luminescent zinc cadmium sulphide and 2 parts of a mixture of the lauric acid mono ester of diethylene glycol and a thinner. This material is ground for 6 hours and into the ground mixture is introduced 17 parts of an alkyd resin solution containing approximately 50% solids. This latter mixture is then ground for one hour and is applied by brush. After allowing to stand for 12 hours, it is treated with a protective coating of methyl methacrylate. When exposed to the accelerated test referred to hereinabove, this coating remained in excellent condition for in excess of 50 hours.

My invention may be employed with other types of coatings such as those applied by spraying. It has been found very effective when coatings have been applied by meansof the so-called silk screening method. These products differ from the product applied by the brushing method principally in being of a different consistency. I have employed the features of my invention to advantage, moreover, when the luminescent pigment is applied by a printing and dusting procedure. In this method the binder or vehicle is applied to a surface by a printing operation and the luminescent material in a generally dry condition is dusted onto the said surface and caused to adhere to the printed area thereof. Employing this technique, I first coat the particles of luminescent material with the partial ester by ball milling with a liquid such as a thinner, dry the ground mixture and then sieve it to produce a powder which for practical purposes is substantially dry. The proportion of partial ester employed and the character thereof are such as to promote the production of a substantially dry powder suitable for dusting.

In general, the amount of partial ester employed in the practice of my invention may suitably comprise approximately 10% by weight based upon the weight of the pigment. The size of the pigment particles, however, has an important bearing upon the proportion of partial ester used, enough being employed to coat the surface of the luminescent pigment. In general, the amount employed with usual pigments should be at least of the order of 3%, and, while there is no upper limit to the amount of partial ester employed except a practical one, in general, the partial ester should not be more than 15 to 20% by weight based upon the weight of the pigment.

In the production of the paint or paint-like material utilizing the features of my invention, the luminescent pigment preferably is ground with the partial ester first so as to obtain substantially an intimate mixture of these two materials and a coating of the pigment particles with the partial ester. Fairly satisfactory results can be obtained however by employing another order of steps and, if desired, all of the ingredients may be incorporated in a ball mill and ground together. Generally speaking, greater grinding time will be required if this method is used.

The vehicle employed for the pigment can be any suitable material. Thus it may be of the lacquer type employing a cellulose derivative or of the paint type employing a drying oil. The vehicle should be of such a character, however, that, in the final product, the substance binding the pigment together will pass at least enough ultra violet light to cause luminescence of the pigment particles. Preferably, however, I prefer a resin, optionally a synthetic weather-resisting resin and preferably an alkyd type of resin which I have found particularly efficacious when employed in combination with the partial ester. The combination of glycerol-mono-ricinoleate and an alkyd resin is particularly satisfactory. By the term alkyd resins I mean to include all weather-resisting resinous substances produced by the condensation of polyhydric alcohols and poly-basic acids and specifically the condensation product of glycerin and phthalic acid.

Hereinabove, in the specific examples iven, I have referred to two specific partial ester which have been employed with good results in the practice of my invention. It must not be assumed, however, that other partial esters of relatively high molecular weight carboxylic acids and polyhydroxy substances cannot also be used with considerable advantage over the prior art. In general, any relatively high molecular weight carboxylic acid containing at least six carbon atoms may be employed to partially esterify a polyhydroxy substance and the resulting partial ester may be used in the practice of my invention. Examples of acids that may be employed in the production of such esters for my invention are straight chain and branched chain, saturated and unsaturated, carboxylic, aliphatic (including cycloaiiphatic), fatty, aromatic, hydroaromatic, and araliphatic acids including caproic acid,

caprylic acid, pelargonic acid, capric acici, sebacic acid, behenlc acid, arachidic acid, cerotic acid, enanthic acid, eruclc acid, melissic acid stearic acid, oleic acid, ricinoleic acid, ricinelaidic acid, riclnostearolic acid, linoleic acid, linolenic acid, lauric acid, myristic acid, palmitic acid, mixtures of any two or more of the above mentioned acids or other acids, mixed higher fatty acids derived from animal or vegetable sources, for example, lard, coconut oil, rapeseed oil, sesame oil, palm kernel oil, palm oil, olive oil, corn oil, cottonseed oil, sardine oil, tallow, soya bean oil, peanut oil, castor oil, seal oils, whale oil, shark oil and other fish oils, partially or completed hydrogenated animal and vegetable oils such as those mentioned; oxidized hydroxy and alpha-hydroxy higher carboxylic, aliphatic and fatty and/or polymerized higher fatty acids or higher fatty acids derived from oxidized and/or polymerized triglyceride oils; acyloxy carboxylic acids such as CiIHse-CO-O-CHa-COOH; acids such as i-hydroxy stearic acid, dihydroxypalmitic acid, di-hydroxystearic acid, dihydroxybehenic acid, alpha-hydroxy capric acid, alpha-hydroxy stearic acid, alpha-hydroxy palmitic acid, alpha-hydroxy lauric acid, alpha-hydroxy myrlstic acid, alphahydroxy coconut oil mixed fatty acids, alpha-,

hydroxy margaric acid, alpha-hydroxy arachidic acid, and the like; fatty and similar acids derived from various waxes such as beeswax, spermaceti, montan wax, coccerin, and carnauba wax and higher molecular weight carboxylic acids derived, by oxidation and other methods, from paraffin wax, petroleum and similar hydrocarbons; resinic and hydroaromatic acids such as hexahydrobenzoic acid, naphthenic acid and abietic acid; araliphatic and aromatic acids such as phthalic acid, benzoic acid, Twitchell fatty acids, naphthoic acid, pyridine carboxylic acid; hydroxy aromatic acids such as salicylic acid, hydroxy benzoic and naphthoic acids, and the like. It will be understood that mixtures of any two or more of said acids may be employed if desired and it will also be appreciated that said acids may contain substituent groups such as sulphate, sulphonic, nitrile, cyanogen, carbonyl, amide, amine, halogen, ketone and other groups. The acids may be employed as such or in the form of their anhydrides, esters including mono-, di-, tri-glycerides and the like, and acyl halides, or, in general, in the form of any of their acylating compounds. Of particular utility are the unsubstituted aliphatic acids containing from twelve to eighteen carbon atoms and their acyl halides.

The aliphatic polyhydroxy substances used in the preparation of the compounds described herein may be selected from a large class and include, among those mentioned, glycerol; glycols such as ethylene glycol, propylene glycol, trimethylene glycol, butylene glycol and the like; polyglycols such as diethylene glycol, triethylene glycol and tetraethylene glycol; pentaerythritol; quercitol; di-hydroxy acetone; triethanolamine; tripropanolamine; polyglycerols such as diglycerol, triglycerol, tetraglycerol and the like including mixtures thereof; carbohydrates and sugars including mono-, diand polysaccharides such as dextrose, sucrose, xylose, arabinose, galactose, fructose, maltose, mannose, dextrin, starch, and the like; the natural and synthetic simple and complex glucosides; sugar alcohols such as arabitol, mannitol, mannitan, sorbitol, sorbitan, and dulcitol; and polyhydroxy-carboxylic acids such as tartaric acid, muclc acid, saccharic acid, gluconic acid, glucuronic acid, gulonic acid, mannonic acid, trihydroxy-glutaric acid, glyceric acid,

carboxylic oxidation products of polyglycerols, others of similar character, and hydroxyethyl and hydroxypropyl ether derivatives of the above, as, for-example:

(For convenience, all hydroxyl groups are written facing one way.)

I shall not identify particular compounds beyond those already mentioned, but any partial esters produced employing the starting materials set out hereinabove may be employed to advantage particularly with synthetic resinous vehicles and preferably with the alkyd resins. I wish to repeat, however, that the partial ester of ricinoleic acid and glycerin has been found to be exceptionally satisfactory, and this particular partial ester in combination with a resin comprising the condensation product of glycerin and phthalic anhydride has been found commercially to be very satisfactory.

In the preceding description, I have referred in several places to the application of the invention to a coating material adapted to be applied in the form of a paint either by brushing or spraying and have indicated that my invention may be utilized with coatings applied in other ways. -I know of no common expression to identify a material adapted to be used as an ink and a material adapted to be used as a paint to be applied with a brush, so for convenience in defining the invention in the claims, I have employed the broad expressionfcoating material. The meaning and significance of this expression when used in the claims is believed to be clear. Other terms, such as resin, are used according to their ordi nary meanings in both the specification and claims except where the context indicates otherwise. I employ the term solvent, however, broadly in the claims to identify either a single solvent or mixtures of solvents functioning as a so-called thinner. My invention, of course, is not particularly concerned with the type of solvents used. I

The features and scope of my invention are defined in the claims.

' carbon atoms and a polyhydroxy substance, said luminescent pigment being of a type affected adversely by moisture and light, said partial ester functioning to retard the adverse effect of moisture and light on the luminescent pigment.

2. A luminescent coating material comprising a vehicle, a luminescent pigment and a partial ester of an aliphatic mono-carboxylic acid containing at least 6 carbon atom and a polyhydric alcohol, said luminescent pigment being of a type affected adversely by moisture and light, said partial ester functioning to retard the adverse effect of moisture and light on the luminescent pigment.

3. A luminescent coating material comprising a resin, a solvent therefor, a luminescent pigment and a partial ester of a mono-carboxylic acid containing at least 6 carbon atoms and a polyhydroxy substance, said luminescent pigment being of a type adversely affected by moisture and light and the partial ester functioning to retard the adverse efiect of moisture and light on the said luminescent pigment.

4. A luminescent coating material comprising an alkyd resin, a solvent therefor, a luminescent pigment and a partial ester of a mono-carboxylic acid containing at least 6 carbon atoms and a polyhydroxy substance, said luminescent pigment being of a type adversely affected by moisture and light and the partial ester functioning to retard the adverse effect of moisture and light on the said luminescent pigment.

5. .A luminescent coating material comprising a resin, a solvent therefor, a luminescent pigment and a partial ester of glycerin and an aliphatic mono-carboxylic acid containing at least 6 carbon atoms, said luminescent pigment being of a type adversely affected by moisture and light and the partial ester functioning to retard the adverse effect of moisture and light on the said luminescent pigment.

6. A luminescent coating material comprising a resin, a olvent therefor, a luminescent pigment and a partial ester of glycerin and ricinoleic acid, said luminescent pigment being of a, type adversely affected by moisture and light and the partial ester functioning to retard the adverse effect of moisture and light on the said luminescent pigment.

7. A luminescent coating material comprising a resin, a. solvent therefor, a luminescent pigment and a partial ester of a polyhydric alcohol and ricinoleic acid, said luminescent pigment being of a type adversely affected by moisture and light and the partial ester functioning to retard the adverse effect of moisture and light on the said luminescent pigment.

8. A luminescent coating material comprising a resin, a solvent therefor, a luminescent pigment and glycerol mono-ricinoleate, said luminescent pigment being of a type adversely affected by moisture and light.

9. A luminescent coating material comprising an alkyd resin, a solvent therefor, a. luminescent pigment and glycerol mono-ricinoleate, said luminescent pigment being of a type adversely affected by moisture and light.

10. A luminescent coating material comprising a resin, a solvent therefor, a luminescent sulphide pigment and a partial ester of a mono-carboxylic acid containing at least 6 carbon atoms and a polyhydroxy substance.

11. A luminescent coating material comprising an alkyd resin, a solvent therefor, a luminescent sulphide pigment and a partial ester of a monocarboxylic acid containing at least 6 carbon atoms and a polyhydroxy substance.

12. A luminescent coating material comprising an alkyd resin, a solvent therefor, a luminescent sulphide pigment and glycerol mono-ricinoleate.

13. A luminescent paint comprising a luminescent sulphide pigment, a binder therefor at least partially transparent to ultra violet light, a solvent for said binder and glycerol mono-ricinoleate, the glycerol mono-ricinoleate comprising 10% by weight based upon the weight of the pigment, and the pigment particles being coated therewith.

14, A luminescent coating material comprising a vehicle, a luminescent pigment, and a fatty acid mono-ester of an aliphatic polyhydric alcohol, the fatty acid radical of which contains at least 6 carbon atoms, said luminescent pigment being of a type affected adversely by moisture and light, said mono-ester functioning to retard the adverse effect of moisture and light on the luminescent pigment.

15. A luminescent coating material comprising an alkyd resin, a solvent therefor, a luminescent sulphide pigment and a fatty acid monoglyceride, the fatty acid radical of which contains at least 6 carbon atoms, said monoglyceride comprising of the order of about 10% by weight of the amount of said pigment.

SAMPSON ISENBERG. 

